Field of the Invention
The present invention relates to an improved catalyst for use in the ammoxidation of an unsaturated hydrocarbon to the corresponding unsaturated nitrile. In particular, the present invention is directed to an improved catalytic composition for the ammoxidation of propylene and/or isobutylene to acrylonitrile and/or methacrylonitrile, respectively, wherein said catalyst comprises a complex of metal oxides comprising rubidium, bismuth, cerium, molybdenum, iron, and other promoters and wherein said catalyst is characterized by ratio of rubidium to bismuth and cerium contained in the catalyst.
Description of the Prior Art
Catalysts containing oxides of iron, bismuth and molybdenum, promoted with suitable elements, have long been used for the conversion of propylene and/or isobutylene at elevated temperatures in the presence of ammonia and oxygen (usually in the form of air) to manufacture acrylonitrile and/or methacrylonitrile. In particular, Great Britain Patent 1436475; U.S. Pat. Nos. 4,766,232; 4,377,534; 4,040,978; 4,168,246; 5,223,469 and 4,863,891 are each directed to bismuth-molybdenum-iron catalysts which may be promoted with the Group II elements to produce acrylonitrile. In addition, U.S. Pat. Nos. 5,093,299, 5,212,137, 5,658,842, 5,834,394, 8,153,546 and CN103418400 are directed to bismuth-molybdenum promoted catalysts exhibiting high yields to acrylonitrile.
In part, the instant invention relates to a bismuth-molybdenum-iron catalysts promoted with cerium. It has been discovered that by controlling the relative ratio of bismuth to cerium impacts the performance of the catalyst.